Evolution of the T Cell Receptor Signal Transduction Units

Abstract

The mammalian T cell receptor (TCR)/CD3 complex has been the focus of intense studies for many years. It consists of six different chains, which form hetero- and homodimers to constitute the complete TCR/CD3 complex (see Bentley and Mariuzza 1996; Lanzavecchia et al. 1999; Terhorst et al. 1995; Wange and Samelson 1996 for recent reviews on different aspects). The clonotypic TCR genes have now been isolated from a number of vertebrate species, including cartilaginous, bony fish, amphibia, and chickens (see Charlemagne et al. 1998; Chen et al. 1995 for review). Paradoxically, information regarding the nonmammalian CD3 genes is limited to three cloned CD3 homologues (Bernot and Auffray 1991; Dzialo and Cooper 1997; Göbel and Fluri 1997) and the chicken ζ chain (Göbel and Bolliger 1998).